Thermostatic liquid bath is widely used in the fields such as petroleum, chemical engineering, electronic instrumentation, physics, chemistry, bioengineering, medical and health, life sciences, light industry food, physical property testing and chemical analysis, and a field source with controlled heat and cold and uniform and constant temperature is provided. The constant temperature test or testing is performed on a test sample or manufactured product, and the thermostatic liquid bath may also be used as a heat source or cold source for directly heating or refrigerating and auxiliary heating or refrigerating. Since the liquid has high density and high heat capacity, and is easy to achieve constant temperature accuracy higher than air or other gas baths, and less susceptible to environmental interference, the thermostatic liquid bath is more widely used than gas bath.
Patent ZL96244411.1, Patent CN201320651525.2, Patent CN200820121106.7, Patent 200910200263.6, Patent 200920214476.X, Patent 201310221426.5, etc., disclose thermostatic bath structures and mediums used thereby, which however, are not applicable to the liquid medium of the temperature −110° C. or below. Some manufacturing companies such as FLUKE, US, also have no related products of the temperature lower than −110° C. The underlying reason is the lack of a suitable liquid medium in such temperature region. The substances such as methane, ethane, propane, butane, R124, R22 and R32 have a very low triple point, and can exist in the form of liquid at −150° C. or even −180° C., but are extremely easy to volatize due to an excessive atmospheric boiling point. Although the commonly used thermostatic bath mediums such as methanol, ethanol and propanol have a relatively high boiling point, and are not easy to volatilize, the viscosity at about −110° C. is very high due to the limitation of the triple point, and the requirement of the uniform temperature of the thermostatic bath cannot be met. Therefore, the demand of the constant temperature on the temperature region of −110° C. and below (such as temperature calibration) is wide, but no relevant products exist on the market yet due to the lack of the liquid medium.